Helicopters are known substantially comprising a fuselage; a main rotor rotating about a first axis and fitted to a top portion of the fuselage; and an antitorque rotor located at the tail end of the helicopter and rotating about a second axis crosswise to the first.
Known helicopters also comprise at least one engine; and a transmission for transmitting motion from the engine to the main rotor.
More specifically, the engine has an intake conduit for a first airflow of fresh air from the outside; and an exhaust conduit for externally discharging high-temperature burnt gas.
The helicopter also comprises a transmission housing; and an inlet connecting the housing to the outside to produce a second airflow of fresh air by which to cool the transmission either directly or with the interposition of a radiator.
The thermodynamic efficiency of the engine and transmission cooling efficiency are affected by the attitude, and particularly the yaw angle, of the helicopter.
That is, flow of the first and second airflow vary alongside variations in the yaw angle of the helicopter.
Variations in yaw angle also affect the degree of turbulence in the first airflow, thus affecting the thermodynamic efficiency of the engine.
A need is felt within the industry to achieve as constant a flow as possible of the first and second airflow, and to minimize turbulence in the first airflow over a wide attitude range, so as to achieve optimum thermodynamic efficiency of the engine and effectively cool the transmission within said range.